Calcium Calcium in the body is 1.1–1.2 kg for the average weight of a healthy man and 900 g for the average weight of a healthy woman. Almost all calcium is found in teeth and bones, with the exception of 1%, which is found in blood, lymph and cells(!). The most famous function of calcium is

Among all the elements of the periodic table, several can be identified, without which not only do various diseases develop in living organisms, but it is generally impossible to live and grow normally. One of these is calcium.

It is interesting that when we talk about this metal as a simple substance, it has no benefit for humans, even harm. However, as soon as you mention Ca 2+ ions, a lot of points immediately arise that characterize their importance.

Position of calcium in the periodic table

The characterization of calcium, like any other element, begins with indicating its location in the periodic table. After all, it makes it possible to learn a lot about a given atom:

• nuclear charge;
• number of electrons and protons, neutrons;
• oxidation state, highest and lowest;
• electronic configuration and other important things.

The element we are considering is located in the fourth major period of the second group, the main subgroup, and has a serial number of 20. Also, the periodic chemical table shows the atomic weight of calcium - 40.08, which is the average value of the existing isotopes of a given atom.

The oxidation state is one, always constant, equal to +2. Formula CaO. The Latin name for the element is calcium, hence the symbol for the Ca atom.

Characteristics of calcium as a simple substance

Under normal conditions, this element is a metal, silvery-white in color. The formula of calcium as a simple substance is Ca. Due to its high chemical activity, it is capable of forming many compounds belonging to different classes.

In a solid state of aggregation, it is not part of the human body, therefore it is important for industrial and technical needs (mainly chemical syntheses).

It is one of the most common metals in the earth’s crust, about 1.5%. It belongs to the alkaline earth group, since when dissolved in water it produces alkalis, but in nature it is found in the form of multiple minerals and salts. A lot of calcium (400 mg/l) is included in sea water.

Crystal cell

The characteristics of calcium are explained by the structure of the crystal lattice, which can be of two types (since there is an alpha and beta form):

• cubic face-centric;
• volume-centric.

The type of bond in the molecule is metallic; at lattice sites, like all metals, there are atom ions.

Being in nature

There are several main substances in nature that contain this element.

1. Sea water.
2. Rocks and minerals.
3. Living organisms (shells and shells, bone tissue, etc.).
4. Groundwater in the earth's crust.

The following types of rocks and minerals can be identified as natural sources of calcium.

1. Dolomite is a mixture of calcium and magnesium carbonate.
2. Fluorite is calcium fluoride.
3. Gypsum - CaSO 4 2H 2 O.
4. Calcite - chalk, limestone, marble - calcium carbonate.
5. Alabaster - CaSO 4 ·0.5H 2 O.
6. Apatity.

In total, there are about 350 different minerals and rocks that contain calcium.

Methods of obtaining

For a long time it was not possible to isolate the metal in its free form, since its chemical activity is high and cannot be found in nature in its pure form. Therefore, until the 19th century (1808), the element in question was another mystery posed by the periodic table.

The English chemist Humphry Davy managed to synthesize calcium as a metal. It was he who first discovered the peculiarities of the interaction of melts of solid minerals and salts with electric current. Today, the most relevant way to obtain this metal is the electrolysis of its salts, such as:

• a mixture of calcium and potassium chlorides;
• a mixture of fluoride and calcium chloride.

It is also possible to extract calcium from its oxide using aluminothermy, a common method in metallurgy.

Physical properties

The characteristics of calcium according to physical parameters can be described in several points.

1. The state of aggregation is solid under normal conditions.
2. Melting point - 842 0 C.
3. The metal is soft and can be cut with a knife.
4. Color - silver-white, shiny.
5. It has good conductive and heat-conducting properties.
6. When heated for a long time, it turns into a liquid, then a vapor state, losing its metallic properties. Boiling point 1484 0 C.

The physical properties of calcium have one peculiarity. When pressure is applied to a metal, at some point in time it loses its metallic properties and ability to conduct electrically. However, with a further increase in exposure, it is restored again and manifests itself as a superconductor, several times higher in these indicators than other elements.

Chemical properties

The activity of this metal is very high. Therefore, there are many interactions that calcium enters into. Reactions with all non-metals are common for him, because as a reducing agent he is very strong.

1. Under normal conditions, it easily reacts to form the corresponding binary compounds with: halogens, oxygen.
2. When heated: hydrogen, nitrogen, carbon, silicon, phosphorus, boron, sulfur and others.
3. In the open air it immediately interacts with carbon dioxide and oxygen, and therefore becomes covered with a gray coating.
4. Reacts violently with acids, sometimes causing inflammation.

Interesting properties of calcium appear when it comes to salts. So, beautiful caves growing on the ceiling and walls are nothing more than formed over time from water, carbon dioxide and bicarbonate under the influence of processes within underground waters.

Considering how active the metal is in its normal state, it is stored in laboratories, just like alkaline metals. In a dark glass container, with a tightly closed lid and under a layer of kerosene or paraffin.

A qualitative reaction to calcium ion is the coloring of the flame in a beautiful, rich brick-red color. You can also identify the metal in the composition of the compounds by the insoluble precipitates of some of its salts (calcium carbonate, fluoride, sulfate, phosphate, silicate, sulfite).

Metal connections

The types of metal compounds are as follows:

• oxide;
• hydroxide;
• calcium salts (medium, acidic, basic, double, complex).

Calcium oxide known as CaO is used to create a building material (lime). If you quench the oxide with water, you get the corresponding hydroxide, which exhibits the properties of an alkali.

Various calcium salts, which are used in different sectors of the economy, are of great practical importance. We have already mentioned above what kind of salts exist. Let us give examples of the types of these connections.

1. Medium salts - carbonate CaCO 3, phosphate Ca 3 (PO 4) 2 and others.
2. Acidic - hydrogen sulfate CaHSO 4.
3. The main ones are bicarbonate (CaOH) 3 PO 4.
4. Complex - Cl 2.
5. Double - 5Ca(NO 3) 2 *NH 4 NO 3 *10H 2 O.

It is in the form of compounds of this class that calcium is important for biological systems, since salts are the source of ions for the body.

Biological role

Why is calcium important for the human body? There are several reasons.

1. It is the ions of this element that are part of the intercellular substance and tissue fluid, participating in the regulation of excitation mechanisms, the production of hormones and neurotransmitters.
2. Calcium accumulates in bones and tooth enamel in an amount of about 2.5% of the total body weight. This is quite a lot and plays an important role in strengthening these structures, maintaining their strength and stability. The growth of the body without this is impossible.
3. Blood clotting also depends on the ions in question.
4. It is part of the heart muscle, participating in its excitation and contraction.
5. It is a participant in the processes of exocytosis and other intracellular changes.

If the amount of calcium consumed is not enough, then diseases such as:

• rickets;
• osteoporosis;
• blood diseases.

The daily intake for an adult is 1000 mg, and for children over 9 years old 1300 mg. In order to prevent an excess of this element in the body, you should not exceed the specified dose. Otherwise, intestinal diseases may develop.

For all other living beings, calcium is no less important. For example, although many do not have a skeleton, their external means of strengthening are also formations of this metal. Among them:

• shellfish;
• mussels and oysters;
• sponges;
• coral polyps.

They all carry on their backs or, in principle, form in the process of life a certain external skeleton that protects them from external influences and predators. Its main component is calcium salts.

Vertebrates, like humans, need these ions for normal growth and development and receive them from food.

There are many options with which it is possible to replenish the missing element in the body. The best, of course, are natural methods - products containing the desired atom. However, if for some reason this is insufficient or impossible, the medical route is also acceptable.

So, the list of foods containing calcium is something like this:

• dairy and fermented milk products;
• fish;
• greenery;
• grains (buckwheat, rice, baked goods made from whole grain flour);
• some citrus fruits (oranges, tangerines);
• legumes;
• all nuts (especially almonds and walnuts).

If you are allergic to some foods or cannot eat them for another reason, then calcium-containing preparations will help replenish the level of the necessary element in the body.

All of them are salts of this metal, which have the ability to be easily absorbed by the body, quickly absorbed into the blood and intestines. Among them, the most popular and used are the following.

1. Calcium chloride - solution for injection or for oral administration to adults and children. It differs in the concentration of salt in the composition; it is used for “hot injections”, since it causes exactly this sensation when injected. There are forms with fruit juice for easier oral administration.
2. Available in both tablets (0.25 or 0.5 g) and solutions for intravenous injection. Often in tablet form it contains various fruit additives.
3. Calcium lactate - available in tablets of 0.5 g.

CALCIUM (Latin Calcium), Ca, chemical element of group II of the short form (group 2 of the long form) of the periodic system; refers to alkaline earth metals; atomic number 20; atomic mass 40.078. There are 6 stable isotopes in nature: 40 Ca (96.941%), 42 Ca (0.647%), 43 Ca (0.135%), 44 Ca (2.086%), 46 Ca (0.004%), 48 Ca (0.187%); radioisotopes with mass numbers 34-54 were artificially obtained.

Historical reference. Many natural calcium compounds were known in ancient times and were widely used in construction (for example, gypsum, lime, marble). Calcium metal was first isolated by G. Davy in 1808 during the electrolysis of a mixture of CaO and HgO oxides and the subsequent decomposition of the resulting calcium amalgam. The name comes from the Latin calx (genitive calcis) - lime, soft stone.

Prevalence in nature. The calcium content in the earth's crust is 3.38% by weight. Due to high chemical activity, it is not found in a free state. The most common minerals are anorthite Ca, anhydrite CaSO 4, apatite Ca 5 (PO 4) 3 (F,Cl,OH), gypsum CaSO 4 2H 2 O, calcite and aragonite CaCO 3, perovskite CaTiO 3, fluorite CaF 2, scheelite CaWO 4 . Calcium minerals are found in sedimentary (such as limestone), igneous, and metamorphic rocks. Calcium compounds are found in living organisms: they are the main components of vertebrate bone tissue (hydroxyapatite, fluorapatite), coral skeletons, mollusk shells (calcium carbonate and phosphates), etc. The presence of Ca 2+ ions determines water hardness.

Properties. The configuration of the outer electron shell of the calcium atom is 4s 2; in compounds it exhibits an oxidation state of +2, rarely +1; Pauling electronegativity 1.00, atomic radius 180 pm, radius of Ca 2+ ion 114 pm (coordination number 6). calcium is a silvery-white soft metal; up to 443 °C the modification with a cubic face-centered crystal lattice is stable, above 443 °C - with a cubic body-centered lattice; melting point 842°C, boiling point 1484°C, density 1550 kg/m 3 ; thermal conductivity 125.6 W/(m K).

Calcium is a metal of high chemical activity (stored in hermetically sealed containers or under a layer of mineral oil). Under normal conditions, it easily interacts with oxygen (calcium oxide CaO is formed), when heated - with hydrogen (CaH 2 hydride), halogens (calcium halides), boron (CaB 6 boride), carbon (calcium carbide CaC 2), silicon (Ca silicides 2 Si, CaSi, CaSi 2, Ca 3 Si 4), nitrogen (nitride Ca 3 N 2), phosphorus (phosphides Ca 3 P 2, CaP, CaP 5), chalcogens (chalcogenides of the composition CaX, where X is S, Se, Those). Calcium interacts with other metals (Li, Cu, Ag, Au, Mg, Zn, Al, Pb, Sn, etc.) to form intermetallic compounds. Calcium metal reacts with water to form calcium hydroxide Ca(OH) 2 and H 2 . Reacts vigorously with most acids, forming the corresponding salts (for example, calcium nitrate, calcium sulfate, calcium phosphates). Dissolves in liquid ammonia to form a dark blue solution with metallic conductivity. When ammonia evaporates from such a solution, ammonia is released. Gradually, calcium reacts with ammonia to form the amide Ca(NH 2) 2. Forms various complex compounds, the most important are complexes with oxygen-containing polydentate ligands, for example Ca complexonates.

Biological role. Calcium is a biogenic element. The daily human need for calcium is about 1 g. In living organisms, calcium ions are involved in the processes of muscle contraction and transmission of nerve impulses.

Receipt. Calcium metal is produced by electrolytic and metallothermic methods. The electrolytic method is based on the electrolysis of molten calcium chloride with a touch cathode or a liquid copper-calcium cathode. Calcium is distilled off from the resulting copper-calcium alloy at a temperature of 1000-1080 °C and a pressure of 13-20 kPa. The metallothermic method is based on the reduction of calcium from its oxide with aluminum or silicon at 1100-1200 °C. This produces calcium aluminate or silicate, as well as calcium gas, which is then condensed. World production of calcium compounds and materials containing calcium is about 1 billion tons/year (1998).

Application. Calcium is used as a reducing agent in the production of many metals (Rb, Cs, Zr, Hf, V, etc.). Calcium silicides, as well as alloys of calcium with sodium, zinc and other metals, are used as deoxidizers and desulfurizers of some alloys and oil, to purify argon from oxygen and nitrogen, and in electric vacuum devices as a gas absorber. CaCl 2 chloride is used as a desiccant in chemical synthesis, gypsum is used in medicine. Calcium silicates are the main components of cement.

Lit.: Rodyakin V.V. Calcium, its compounds and alloys. M., 1967; Spitsyn V.I., Martynenko L.I. Inorganic chemistry. M., 1994. Part 2; Inorganic chemistry / Edited by Yu. D. Tretyakov. M., 2004. T. 2.

L. N. Komissarova, M. A. Ryumin.

Calcium- element of the 4th period and PA group of the Periodic Table, serial number 20. Electronic formula of the atom [ 18 Ar]4s 2, oxidation states +2 and 0. Refers to alkaline earth metals. It has low electronegativity (1.04) and exhibits metallic (basic) properties. Forms (as a cation) numerous salts and binary compounds. Many calcium salts are slightly soluble in water. In nature - sixth In terms of chemical abundance, the element (third among metals) is found in a bound form. A vital element for all organisms. The lack of calcium in the soil is compensated by applying lime fertilizers (CaC0 3, CaO, calcium cyanamide CaCN 2, etc.). Calcium, calcium cation and its compounds color the flame of a gas burner dark orange ( qualitative detection).

Calcium Ca

Silvery-white metal, soft, ductile. In humid air it fades and becomes covered with a film of CaO and Ca(OH) 2. Very reactive; ignites when heated in air, reacts with hydrogen, chlorine, sulfur and graphite:

Reduces other metals from their oxides (an industrially important method - calciumthermia):

Receipt calcium in industry:

Calcium is used to remove non-metal impurities from metal alloys, as a component of light and anti-friction alloys, and to separate rare metals from their oxides.

Calcium oxide CaO

Basic oxide. Technical name: quicklime. White, very hygroscopic. It has an ionic structure Ca 2+ O 2- . Refractory, thermally stable, volatile when ignited. Absorbs moisture and carbon dioxide from the air. Reacts vigorously with water (with high exo- effect), forms a strongly alkaline solution (a hydroxide precipitate is possible), a process called lime slaking. Reacts with acids, metal and non-metal oxides. It is used for the synthesis of other calcium compounds, in the production of Ca(OH) 2, CaC 2 and mineral fertilizers, as a flux in metallurgy, a catalyst in organic synthesis, and a component of binding materials in construction.

Equations of the most important reactions:

Receipt Sao in industry— limestone firing (900-1200 °C):

CaCO3 = CaO + CO2

Calcium hydroxide Ca(OH) 2

Basic hydroxide. Technical name is slaked lime. White, hygroscopic. It has an ionic structure: Ca 2+ (OH -) 2. Decomposes when heated moderately. Absorbs moisture and carbon dioxide from the air. Slightly soluble in cold water (an alkaline solution is formed), and even less soluble in boiling water. A clear solution (lime water) quickly becomes cloudy due to the precipitation of hydroxide precipitate (the suspension is called milk of lime). A qualitative reaction to the Ca 2+ ion is the passage of carbon dioxide through lime water with the appearance of a CaCO 3 precipitate and its transition into solution. Reacts with acids and acid oxides, enters into ion exchange reactions. It is used in the production of glass, bleaching lime, lime mineral fertilizers, for causticizing soda and softening fresh water, as well as for preparing lime mortars - dough-like mixtures (sand + slaked lime + water), serving as a binding material for stone and brickwork, finishing ( plastering) walls and other construction purposes. The hardening (“setting”) of such solutions is due to the absorption of carbon dioxide from the air.

History of calcium

Calcium was discovered in 1808 by Humphry Davy, who, by electrolysis of slaked lime and mercuric oxide, obtained calcium amalgam, as a result of the process of distilling mercury from which the metal remained, called calcium. In Latin lime sounds like calx, it was this name that was chosen by the English chemist for the discovered substance.

Calcium is an element of the main subgroup II of group IV of the periodic table of chemical elements D.I. Mendeleev, has an atomic number of 20 and an atomic mass of 40.08. The accepted designation is Ca (from the Latin - Calcium).

Physical and chemical properties

Calcium is a reactive soft alkali metal with a silvery-white color. Due to interaction with oxygen and carbon dioxide, the surface of the metal becomes dull, so calcium requires a special storage regime - a tightly closed container, in which the metal is filled with a layer of liquid paraffin or kerosene.

Calcium is the most well-known of the microelements necessary for humans; the daily requirement for it ranges from 700 to 1500 mg for a healthy adult, but it increases during pregnancy and lactation; this must be taken into account and calcium must be obtained in the form of preparations.

Being in nature

Calcium has very high chemical activity, therefore it is not found in nature in its free (pure) form. However, it is the fifth most common in the earth's crust; it is found in the form of compounds in sedimentary (limestone, chalk) and rocks (granite); feldspar anorite contains a lot of calcium.

It is quite widespread in living organisms; its presence has been found in plants, animals and humans, where it is present mainly in teeth and bone tissue.

Calcium absorption

An obstacle to the normal absorption of calcium from food is the consumption of carbohydrates in the form of sweets and alkalis, which neutralize the hydrochloric acid of the stomach, which is necessary to dissolve calcium. The process of calcium absorption is quite complex, so sometimes it is not enough to get it only from food; additional intake of the microelement is necessary.

Interaction with others

To improve the absorption of calcium in the intestine, it is necessary, which tends to facilitate the process of calcium absorption. When taking calcium (in the form of supplements) while eating, absorption is blocked, but taking calcium supplements separately from food does not affect this process in any way.

Almost all of the body's calcium (1 to 1.5 kg) is found in bones and teeth. Calcium is involved in the processes of excitability of nervous tissue, muscle contractility, blood clotting processes, is part of the nucleus and membranes of cells, cellular and tissue fluids, has anti-allergic and anti-inflammatory effects, prevents acidosis, and activates a number of enzymes and hormones. Calcium is also involved in the regulation of cell membrane permeability and has the opposite effect.

Signs of calcium deficiency

Signs of calcium deficiency in the body are the following, at first glance, unrelated symptoms:

• nervousness, worsening mood;
• cardiopalmus;
• convulsions, numbness of extremities;
• slowing of growth and children;
• high blood pressure;
• splitting and brittleness of nails;
• joint pain, lowering the “pain threshold”;
• heavy menstruation.

Causes of calcium deficiency

Causes of calcium deficiency may include unbalanced diets (especially fasting), low calcium content in food, smoking and addiction to coffee and caffeine-containing drinks, dysbacteriosis, kidney disease, thyroid disease, pregnancy, lactation and menopause.

Excess calcium, which can occur with excessive consumption of dairy products or uncontrolled use of drugs, is characterized by extreme thirst, nausea, vomiting, loss of appetite, weakness and increased urination.

Uses of calcium in life

Calcium has found application in the metallothermic production of uranium, in the form of natural compounds it is used as a raw material for the production of gypsum and cement, as a means of disinfection (well-known bleach).